Such a system is used in particular in the field of industrial automation. Industrial controllers with a modular configuration are frequently sub-divided into terminal modules and function modules to fit these (digital or analog inputs or outputs, counters and other specialist modules). The wiring can thus be put in place after the terminal-bearing terminal modules have been lined up next to each other. The terminal modules are responsible both for coupling peripheral signals and for forwarding internal control signals. Because of their function, specific types of terminal modules are necessary and possible:
Supply modules, which allow a supply voltage to be supplied for digital I/O functions (opening of a potential group for digital function modules, which are to be supplied from a network device),
Forwarding modules, which forward the supply voltage to the next terminal module and make it available to the function module (where the next digital I/O module is to be supplied by the same network device),
Loop-through modules, which forward the supply voltage to the next terminal module but do not make it available to the function module (where one or more analog function modules are required at a point but the potential group is not to be cleared so no new supply module is then to be used),
Separator modules, which do not forward the supply voltage (analog function modules or specialist modules can be mounted here) and
Specialist modules, which contain a temperature sensor for example to measure the terminal reference temperature.
The mounting of the function modules completes the controller according to the planned function scope. A modular structure of this type allows the degree of expansion of the controller to be tailored relatively precisely to the control tasks required locally, particularly when used in a decentralized instance.